On Thursday, September 20, a Robert Mapplethorpe exhibition titled “Pictures” opened at the Serralves Foundation Museum of Contemporary Art in Porto, Portugal, with 159 works by the photographer, including portraits, still lifes, and other imagery. However, 20 works originally intended for the show were not present, for reasons that remain unclear. One day after the opening, on Friday, João Ribas, the museum’s artistic director, announced his resignation, and an open letter has circulated accusing the institution of censorship. The Mapplethorpe Foundation, in response, has pushed back against that claim.

While Ribas’s reasons for leaving the institution are unclear (attempts to reach him have not yet been successful), reports by Spanish and Portuguese publications attributed his resignation to a stipulation by the museum’s board that a disclaimer be posted in reference to sexually explicit works, among them prints featuring S&M imagery. The disclaimer text reads: “We would like to draw attention to the provocative and possibly shocking nature of the sexual imagery in some of the works on display. Only persons aged 18 and over may enter this room,” according to an image from the exhibition reproduced in the Madrid-based newspaper El País. In interviews leading up to the show, Ribas had said that Mapplethorpe’s more sexually explicit work would be shown alongside his other work without restrictions.

The open letter, addressed to the Serralves Foundation’s president, Ana Pinho, alleges that the show’s restriction was imposed “against the will of its curator,” Ribas, who became the Serralves Foundation Museum’s artistic director in January after having served as chief curator and deputy director since 2014.

In a statement published in part by El País, the Serralves Foundation denied that it had removed any work from the exhibition and said that Ribas himself selected all of the art in the show. The newspaper’s report says that the removal of the 20 works was a curatorial decision by Ribas. “From the beginning,” the statement reads, “the proposal of the exhibition was to present the works of an explicit sexual nature in an area with restricted access, given the tenor of several exhibited works and being that Serralves is an institution visited annually by almost a million people of all backgrounds, ages and nationalities, including thousands of children and hundreds of schools, the foundation considered that the visiting public should be alerted, in accordance with the legislation in force.”

The open letter in support of Ribas reads, in part, “It is with sadness that we continue to see [Mapplethorpe’s] work being apparently censored by institutions such as Serralves on—we suspect—a purely moral basis.” Noting the museum’s mention of Portuguese pornography laws in its decision-making around the exhibition, it goes on to state that many canonical works from throughout Western art history have subjects that could be perceived as pornographic and that such work had “previously displayed in your museum without equal enforcement of age restrictions.”

The open letter, which has since been closed, was signed by some 400 arts professionals, including artists Tania Bruguera, Barbara Hammer, Lynn Hershman Leeson, Carlos Motta, A. L. Steiner, and Wolfgang Tillmans, as well as curators Stuart Comer (of the Museum of Modern Art in New York), Ann Gallagher (of the Tate in London), and Cuauhtémoc Medina (of the Museo Universitario Arte Contemporáneo in Mexico City). A message at the top of the letter notes that it had been officially sent to be Pinho.

In a statement sent to ARTnews made in response to Ribas’s departure, the Mapplethorpe Foundation said there has been “a lot of unnecessary confusion in Porto,” noting that some works were edited out of the exhibition during the installation process “for reasons of exhibition design, repetition, etc.”

“We do not believe that any censorship occurred,” the Mapplethorpe Foundation said. “The restrictive signs posted outside the two smaller galleries reflect the decision of the board of the Serralves.” The foundation said that it has never taken a position “to impose on any community a requirement to exhibit or not exhibit, to restrict or not restrict, or how to restrict entrance. We try not to interfere with any curatorial decisions nor with any museum’s internal issues.”

The Mapplethorpe Foundation’s statement also questioned the “dramatic timing” of Ribas’s resignation, adding that it took away from “the high quality of Mr. Ribas’ exhibition and the importance of the artist.”

As the open letter states, Mapplethorpe’s work has long been a target for censorship and political recriminations. In 1989, months after the celebrated photographer died of AIDS-related causes at the age of 42, a planned show of his work was canceled by officials at the Corcoran Gallery of Art in Washington, D.C., just weeks before it opened.

The Corcoran’s leadership feared that the exhibition, which included works from Mapplethorpe’s “X Portfolio,” a series of 13 sadomasochistic photographs, as well as others with sexually frank subjects, would receive sustained protests and attacks from conservatives like Republican senator Jesse Helms, since it had received funding from the National Endowment for the Arts, which many on the right had regularly attacked for supporting “obscene” art. (Earlier that year, Helms had also similarly denounced the work of Andres Serrano, who had received an NEA artist grant—that program was effectively defunded as a result.)

At the time, artists and activists alleged censorship and protested the Corcoran’s decision to shut down the show. In 1990, it traveled to the Contemporary Arts Center in Cincinnati, where prosecutors charged the museum and its then director with obscenity for displaying the “X Portfolio.” They were later acquitted by a jury.

In 2016, the “X Portfolio” appeared in full at the J. Paul Getty Museum in Los Angeles, as part of a two-venue retrospective held in partnership with the Los Angeles County Museum of Art. That presentation, which also included an advisory at the entrance of the gallery with the “X Portfolio” for its graphic content, drew no protests.

On Wednesday, September 26, just after 11 p.m. in Portugal, the board of directors of the Serralves Foundation released a statement to the press aiming to set the record straight about controversy surrounding the Mapplethorpe exhibition. In a lengthy statement that included a seven-point breakdown of the situation, the board said that the controversy “has been based on false information and misleading allegations,” and it “regrets the lack of careful consideration and the artificial nature of the controversy surrounding this exhibition.” The two main facts in dispute, as acknowledged by the statement, are the removal of 20 works from the exhibition and the creation of a separate space to exhibit some of Mapplethorpe’s more graphic images. The board affirmed that those 20 works were withheld from the exhibition at the discretion of Ribas, and that “[i]t was the Museum Director himself who proposed that the Robert Mapplethorpe’s exhibition should have a reserved area, at the end of the exhibition, dedicated to the most sensitive works. He also proposed that there should be a sign at the entrance to this reserved space clarifying its specific content. The Board of Directors agreed and continues to agree with this proposal.”